It is known to provide axial and radial magnetic bearings in rotary machines having a vertical rotor arrangement and to provide auxiliary mechanical touch down bearings supporting the rotor in case of failure of the magnetic bearings, for example if the magnetic bearings are overloaded or if the electrical or electronic control system fails.
Magnetic bearings operate without mechanical friction, but require continuous supply of electrical power.
Furthermore, rotary machines having constant, unidirectional thrust load, such as for example flywheels, only requires good dynamic performances of the radial magnetic bearings. Indeed, the axial magnetic bearing only supports the rotor weight.
One aim of the present invention is to provide a rotary machine without such axial magnetic bearing in order to reduce manufacturing costs of such rotary machine as well as electrical power consumption.
There is a need to define and dimension correctly auxiliary mechanical touch down bearings so as to fully guarantee that the rotary machine will not be damaged.